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    Posted: March 07 2019 at 2:16pm
Climate change: Rain melting Greenland ice sheet 'even in winter'
By David Shukman
Science editor
8 hours ago
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Image copyrightJOSEPH COOK
Image caption
After it rains the surface darkens, which speeds up melting
Rain is becoming more frequent in Greenland and accelerating the melting of its ice, a new study has found.

Scientists say they're "surprised" to discover rain falling even during the long Arctic winter.

The massive Greenland ice-sheet is being watched closely because it holds a huge store of frozen water.

And if all of that ice melted, the sea level would rise by seven metres, threatening coastal population centres around the world.

Precipitation usually falls as snow in winter - rather than as rain - which can balance out any melting of the ice in the summer.

What did the scientists find?
The scientists studied satellite pictures of the ice-sheet which reveal the areas where melting is taking place.

And they combined those images with data gathered from 20 automated weather stations that recorded when rainfall occurred.

The findings, published in the journal The Cryosphere, show that while there were about two spells of winter rain every year in the early phase of the study period, that had risen to 12 spells by 2012.

On more than 300 occasions between 1979-2012, the analysis found that rainfall events were triggering a melting of the ice.

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Most of these were in summertime, when the air often gets above zero.

But a growing number happened in winter months when the permanent dark of the polar winter would be expected to keep temperatures well below freezing.

What happens when it rains?
Image copyrightJOSEPH COOK
Image caption
The ice after rain in the Kangerlussuaq region, Greenland
The lead author of the study, Dr Marilena Oltmanns of the GEOMAR ocean research centre in Germany, told BBC News: "We were surprised that there was rain in the winter.

"It does make sense because we're seeing flows of warm air coming up from the South, but it's still surprising to see that associated with rainfall."

Another scientist on the study, Prof Marco Tedesco of Columbia University in New York, said that the increase in rain had important implications.

Even if it falls during winter, and then quickly refreezes, the rain changes the characteristics of the surface, leaving it smoother and darker, and "pre-conditioned" to melt more rapidly when summer arrives.

The darker the ice is, the more heat it absorbs from the Sun - causing it to melt more quickly.

"This opens a door to a world that is extremely important to explore," Prof Tedesco said.

"The potential impact of changes taking place in the winter and spring on what happens in summer needs to be understood."

A smoother surface, particularly a "lens" of ice, will allow meltwater to flow over it much faster and being darker means that more of the Sun's rays are absorbed, further speeding-up the warming process.

Pictures taken by a British research team, caught in a rainstorm on the ice-sheet last year, show how a bright highly reflective landscape of snow and ice was turned into a much darker scene.

Why does this matter?
Although Greenland is extremely remote, a vast island lying at the northern end of the Atlantic Ocean, the sheer volume of ice covering it means its fate could have global repercussions.

Image copyrightARWYN EDWARDS
Image caption
The Greenland ice sheet in rainy conditions in 2014
In stable times, snowfall in winter will balance any ice melted or breaking off into the ocean in summer. But research has shown how in recent decades the ice-sheet has been losing vast amounts of mass.

Although this contributes only a relatively small amount to the rise in the sea-level - with much of the rest coming from thermal expansion as the oceans warm - the fear is that the flow of meltwater could accelerate as temperatures rise.

Two years ago, the BBC reported from Greenland on the risks of faster melting, because of the growth of algae which makes the ice darker and more likely to warm.

This effect of algae is, in addition to darkening, caused by soot and other forms of pollution carried by winds to the Arctic.

This comes amid growing concern that the region as a whole is warming twice as fast as the rest of the planet, which may be influencing the flow of the high-altitude jet stream.

That could disturb weather patterns in Europe and other regions, and may also explain how the flows of warm, moist air from the Atlantic are reaching Greenland, even in winter.

What do other scientists make of this?
Prof Jason Box, a glaciologist not involved in the new study, says the research builds on earlier work by him and colleagues published in 2015 that found that summer rainfall could increase the rate of melting.

Their analysis found that because water has a high heat content, it takes only 14mm of rain to melt 15cm of snow, even if that snow is at a temperature of minus 15C.

"There's a simple threshold, the melting point, and when the temperature goes above that you get rain instead of snow," he said.

"So, in a warming climate it's not rocket science that you're going to have more rain than snow, and it's one more reason why the ice sheet can go into deficit instead of being in surplus."

Prof Box has himself experienced sudden rainstorms while camped on the ice-sheet.

"After weeks of sunshine, it started raining on us and it completely transformed the surface - it got darker.

"And I became convinced - only by being there and seeing it with my own eyes - that rain is just as important as strong sunny days in melting the Greenland ice sheet."

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Technophobe Quote  Post ReplyReply Direct Link To This Post Posted: April 24 2019 at 1:34pm
Greenland Is Falling Apart

Since 1972, the giant island’s ice sheet has lost 11 quadrillion pounds of water.   Robinson Meyer   Apr 23, 2019


NASA researchers burn leftover wood on the Helheim Glacier, which is one of the fastest-moving ice floes in Greenland.Lucas Jackson / Reuters

The Greenland Ice Sheet is the world’s second-largest reservoir of fresh water sitting on the world’s largest island. It is almost mind-bogglingly huge.

If Greenland were suddenly transported to the central United States, it would be a very bad day for about 65 million people, who would be crushed instantly. But for the sake of science journalism, imagine that Greenland’s southernmost tip displaced Brownsville, Texas—the state’s southernmost city—so that its icy glaciers kissed mainland Mexico and the Gulf thereof. Even then, Greenland would stretch all the way north, clear across the United States, its northern tenth crossing the Canadian border into Ontario and Manitoba. Kansas City, Oklahoma City, and Iowa City would all be goners. So too would San Antonio, Memphis, and Minneapolis. Its easternmost peaks would slam St. Louis and play in Peoria; its northwestern glaciers would rout Rapid City, South Dakota, and meander into Montana. At its center point, near Des Moines, roughly two miles of ice would rise from the surface.

Suffice it to say: The Greenland Ice Sheet, which contains enough water to refill the Great Lakes 115 times over, is very large. And it is also falling apart.

A new study finds that the Greenland Ice Sheet added a quarter inch of water to global sea levels in just the past eight years. The research, published Monday in the journal Proceedings of the National Academy of Sciences, covers nearly 20 years previously not included in our detailed understanding of the troubled Greenland Ice Sheet. It finds that climate change has already bled trillions of tons of ice from the island reservoir, with more loss than expected coming from its unstable northern half.

“The glaciers are still being pushed out of balance,” Eric Rignot, a senior scientist at NASA and an author of the paper, told me. “Even though the ice sheet has [sometimes] been extremely cold and had low surface melt in the last year, the glaciers are still speeding up, and the ice sheet is still losing mass.”

The paper casts the transformation of the Greenland Ice Sheet as one of the profound geological shifts of our time. Scientists measure the mass of ice sheets in “gigatons”—each unit equal to 1 billion metric tons, or roughly the same amount of water that New York or Los Angeles uses in a year. Greenland, according to the study, has lost 4,976 gigatons of water since 1972. That’s enough water to fill 16 trillion bathtubs or 1.3 quadrillion gallon jugs. That much water weighs about 11 quadrillion pounds. (A quadrillion is 1 with 15 zeros after it.)

More worryingly, the paper finds that Greenland lost about half of that ice—roughly 2,200 gigatons—in the years between 2010 and 2018. The ice sheet has also failed to gain mass in any year since 1998.

This melting isn’t happening at a steady pace, in other words. Greenland’s demise seems to be accelerating. Think of Greenland as a huge inland ice sea, surrounded by faster-moving ice rivers (which are glaciers) that empty the sea and carry ice to the ocean. The paper finds that those rivers are speeding up, carrying ice out of the island’s core nearly twice as fast now as they did in the 1990s or 2000s.

Read: Ancient Rome’s collapse is written into Arctic ice

That’s an alarming result, because it means glaciers might now be shrinking Greenland from the bottom faster than hot weather can melt it from the top. And researchers believe that bottom-melting glaciers are less stable and more prone to rapid collapse. “If there’s a risk of rapid sea-level rise in the future, it will be associated with glaciers speeding up, and not anything happening at the surface,” Rignot said.

The paper’s findings are stirring in part because they go much further back in time. “A lot of the publications [about Greenland’s mass] start in 2000 or 2002, some go back to 1992, but this is the first time we go back another 20 years,” Rignot said. Historically, most studies of Greenland combine data from radar flybys, GPS beacons, and laser or gravity-sensing satellites. But there’s not enough data from before 1992 to be useful, so that’s when estimates usually stop.

Rignot and his colleagues helped hit upon a new resource. The U.S. Geological Survey’s Landsat satellites have circled the planet nonstop since 1972, imaging every speck of land on Earth every 16 days. This archive—which is a kind of Earth-science version of taking a photo of yourself every day for years—includes hundreds of images of Greenland. Rignot and his team taught a computer how to read those pictures of its icy surface, zooming in especially on the dozens of glaciers that connect the interior ice sheet to the sea.

“It’s looking at two different pictures of a glacier, before and after. [In each frame,] the rocks don’t move but the glacier moves, so it can compare and cross-correlate image points,” Rignot said. “Then the algorithm searches around the window for where the pixel might have gone.”

Read: Studying Greenland’s ice to understand climate change

The team ultimately used this technique to calculate the speed of Greenland’s glaciers from 1972 to 1992. Then they combined that data with modern observations of the ice sheet to estimate its historical mass. (They used a similar method to estimate Antarctica’s ice loss in a paper published earlier this year.)

Rignot and his colleagues relied on another new resource too: OMG!

As in, literally, the project is named OMG, short for Oceans Melting Greenland. OMG is a five-year NASA mission, started in 2016, to study how warmer oceans are eroding Greenland’s waterfront glaciers. Rignot helps lead it. “Thanks to OMG, we’ve been able to construct a [bedrock] model of Greenland that is pretty good under the ice, and is very, very good underneath the ocean,” he said.

Brad Lipovsky, a glaciologist at Harvard who was not connected to the research, said in an email that the results “seem plausible at first glance,” but that scientists would need to carefully check some of the team’s methodology. The overall story of Greenland, he said, is that the ice sheet’s flow is slowly accelerating. This “makes sense,” he said, “because it takes the slowly flowing ice sheet a lot longer to respond than the rapidly evolving atmosphere.”

Rignot believes that the new study should make glaciologists look anew at the speed with which Greenland could collapse. The ice sheet’s bleeding-out could eventually raise global sea levels by as much as 25 feet. So the key question, Rignot said, is “How fast can you make these entities fall apart?” The answer will matter to all of us. The surface of Greenland doesn’t have to move through magic to other parts of the world—already, today, its deluge is on its way

Source:   https://www.theatlantic.com/science/archive/2019/04/how-much-ice-has-greenland-lost-climate-change/587431/?utm_source=Nature+Briefing&utm_campaign=26855a4182-briefing-dy-20190424&utm_medium=email&utm_term=0_c9dfd39373-26855a4182-43962649
Absence of proof is not proof of absence.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Josh Quote  Post ReplyReply Direct Link To This Post Posted: April 26 2019 at 2:31am
DJ-Another Greenland article. Melt can also be caused by wind eroding the ice and snow and transporting it into warmer seawater. Increased melt make-sometimes-glaciers "grow" while in fact it is a sign of increased transport of melting ice.
Another growing problem is earth/icequakes. Direct; moving the ice, indirect; tsunamiwaves. Also warmer seawater is making the region warmer.

http://www.thebigwobble.org/2019/04/greenland-is-falling-apart-11.html

Greenland is falling apart! 11 QUADRILLION POUNDS of water lost since 1972 and 286 BILLION TONS of ice lost since 2010 and it's getting worse.

Since 1972, the giant island’s ice sheet has lost 11 quadrillion pounds of water.
The Greenland ice sheet contains enough water to fill the Great Lakes 115 times over - and it's falling apart quicker than ever.
To get a feel of how large Greenland's ice sheet is, it's about three times bigger than Texas, or six times bigger than Germany.
We knew the ice was melting faster and faster - after all, just last year, a study found that the 2012 melting was 4 times faster than in 2003. Now, another study published in PNAS adds even more context, finding that Greenland ice melting has accelerated by 6 times since the 1980s.
Between 1980 and 1990, Greenland lost 51 billion tons of ice - an enormous quantity in its own right. However, in only 8 years, from 2010 to 2018, it lost 286 billion tons.
The losses are expected to get even worse, says Eric Rignot, Ph.D., a professor at the University of California, Irvine, and lead author of the new study.
"Going from a 20-year-long record to a 40-year-long record shows us a transition from a climate dominated by natural variability to a climate dominated by climate warming from human emissions of greenhouse gases," Rignot says.
"Over that time period, the mass loss increased sixfold."
We've seen the effects of rising temperatures in Greenland before.
It's impressive to see a big glacier calve and break away, but most of the time, the melting is far less dramatic - a steady melt and drip over the (still) glacial surface.
Greenland as a whole has already experienced a warming of 2 degrees Celsius (3.6 degrees Fahrenheit), and some areas have warmed by as much as 4 degrees Celsius, this being the main reason for the melting.
The importance of this cannot be overstated.
If all of the Greenland Ice Sheet melted, the sea level would rise by about 20 feet - but that's not even the main concern.
As ice and snow melt, they will leave room to darker soils, which will absorb even more solar energy, further accelerating heating.
Also, even if only a fraction of that sea level rise is achieved, the consequences will be devastating. At this point, no matter what we do, some melting and sea level rise is unavoidable.
But the consequences can range from serious to absolutely devastating if we continue in the business-as-usual scenario.
It's up to us whether we do something to limit the damage.


"If we do something now, it will take 30 years to affect the climate and another few decades to turn the meltdown of glaciers, so probably half of that signal is already written in stone," says Ringot. "But the impact sea level will have on humanity increases with every 10 [centimetres] of sea level rise, and right now we are about to commit to multi-meter sea level rise in the coming century if we don't do something drastic."

DJ-Even when you do not believe "we can save the world", "we passed the last station" we-as humans-have a moral obligation to do everything we can to give next generations, other species, a chance to live.

Greenland has 3 km of ice on it-when the ice will go away Greenland will lift 1 km. This in itself will cause earthquakes and sealevelrise (above the melt of the ice).
We cannot solve our problems with the same thinking we used when we created them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dutch Josh Quote  Post ReplyReply Direct Link To This Post Posted: May 12 2019 at 3:44am
https://www.youtube.com/watch?v=rk4sTnfsVcQ&pbjreload=10 and https://www.youtube.com/watch?v=Ukc7-OVMx_Q

Robert Scribler on the (ant)arctic melt of sea-ice (record low)
We cannot solve our problems with the same thinking we used when we created them.
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